The amazing thing is that one guy is behind everything you see and hear. Dr Pigeon is like a polymath. He develops and runs the site, creates all the sounds and plays all the instruments (with a few exceptions). I beg everyone who uses that site to donate, so he can keep going.
For multi-track recording, you’ll want a DAW. The best free DAWs, IMO, are Reaper and Cakewalk. Personally, I prefer Cakewalk for several reasons but mainly because I don’t like Reaper’s UI. Although, Reaper has a portable version which is super nice.
I still advice you to run the final mix through Audacity, though, since I find its processors superior for mastering than Reaper’s or Cakewalk’s built-in ones.
Safari. I like the way it integrates natively with Passwords and Hide My E-mail and stuff. I don’t really use it that much to care about extensions.
Look at Blender and MediaWiki (the software running Wikipedia). They’re both FOSS and are developed and maintained by volunteers, backed by the end users. They’ve become such a big part of people’s lives, both professionally and privately, that they’ve become the mainstream choice.